A better understanding of the brain mechanisms associated with anxiety and how they are affected by minor tranquilizers may permit more effective treatment of this condition and the development of more specific anti-anxiety agents to minimize the abuse of these compounds by humans. This research proposal is for investigations of the neurochemical changes that occur in the brains of animals exposed to a stressful situation resulting in anxiety. The objectives of the research are: a) to study changes in neurotransmitter systems during the acquisition and extinction of an animal model for anxiety; and b) to concurrently study the acute and chronic effects of minor tranquilizers on the behavior and neurotransmitter systems. The animal model consists of inducing the conditioned emotional response (conditioned suppression of positively reinforced responding) in rats and measuring changes in the turnover of biogenic amines (serotonin, dopamine, norepinephrine and acetylcholine) in brain areas which interact to process emotion. Since benzodiazepines, barbiturates, meprobamate and alcohol are known to act on neurotransmitter systems in naive animals, it is important to establish their role in reversing conditioned suppression, since these drugs have their tranquilizing effect due to a complex interaction between neurochemistry and individual components of the anxiety-producing environment.